U.S. patent application number 14/299507 was filed with the patent office on 2014-12-11 for correcting apparatus for timing recovery of receiver and method thereof.
The applicant listed for this patent is MStar Semiconductor, Inc.. Invention is credited to Chih-Cheng Kuo, Ching-Fu Lan, Tai-Lai Tung.
Application Number | 20140362963 14/299507 |
Document ID | / |
Family ID | 52005480 |
Filed Date | 2014-12-11 |
United States Patent
Application |
20140362963 |
Kind Code |
A1 |
Kuo; Chih-Cheng ; et
al. |
December 11, 2014 |
CORRECTING APPARATUS FOR TIMING RECOVERY OF RECEIVER AND METHOD
THEREOF
Abstract
A correcting apparatus for timing recovery of a receiver is
provided. The receiver includes a timing recovery module that
outputs a first symbol and a second symbol. The correcting
apparatus includes: a channel impulse response module, configured
to generate a first set of peak times and a second set of peak
times according to the first symbol and the second symbol,
respectively; and a calculation module, configured to calculate a
correction signal according to a relationship between the first and
second sets of peak times and to send the correction signal to the
timing recovery module.
Inventors: |
Kuo; Chih-Cheng; (Hsinchu
County, TW) ; Lan; Ching-Fu; (Hsinchu County, TW)
; Tung; Tai-Lai; (Hsinchu County, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MStar Semiconductor, Inc. |
Hsinchu Hsien |
|
TW |
|
|
Family ID: |
52005480 |
Appl. No.: |
14/299507 |
Filed: |
June 9, 2014 |
Current U.S.
Class: |
375/375 |
Current CPC
Class: |
H04L 7/0079 20130101;
H04L 27/2663 20130101; H04L 7/0062 20130101; H04L 27/2671 20130101;
H04L 7/0016 20130101; H04L 27/2695 20130101; H04L 7/0054 20130101;
H04L 27/2675 20130101; H04L 7/027 20130101; H04L 25/0212
20130101 |
Class at
Publication: |
375/375 |
International
Class: |
H04L 7/00 20060101
H04L007/00; H04L 7/027 20060101 H04L007/027 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 11, 2013 |
TW |
102120762 |
Claims
1. A correcting apparatus for timing recovery of a receiver, the
receiver comprising a timing recovery module that outputs a first
symbol and a second symbol, the correcting apparatus comprising: a
channel impulse response module, configured to generate a first set
of peak times and a second set of peak times according to the first
symbol and the second symbol, respectively; and a calculation
module, configured to calculate a correction signal according to a
relationship between the first set of peak times and the second set
of peak times, and to send the correction signal to the timing
recovery module.
2. The correcting apparatus according to claim 1, wherein the
calculation module respectively determines a first peak time and a
second peak time from the first set of peak times and the second
set of peak times according to the relationship between the first
set of peak times and the second set of peak times, and calculates
the correction signal according to a time difference between the
first peak time and the second peak time.
3. The correcting apparatus according to claim 2, wherein a
correction amount corresponding to the correction signal is
directly proportional to the time difference between the first peak
time and the second peak time.
4. The correcting apparatus according to claim 2, wherein the first
peak time and the second peak time are times having largest
responses in the first set of peak times and the second set of peak
times, respectively.
5. The correcting apparatus according to claim 2, wherein a
relative position of the first peak time in the first set of peak
times is same as a relative position of the second peak time in the
second set of peak times.
6. The correcting apparatus according to claim 1, wherein the first
symbol and the second symbol are pilot signals.
7. The correcting apparatus according to claim 1, wherein the first
set of peak times and the second set of peak times are times
corresponding to a plurality of peaks higher than a threshold when
channel impulse responses are calculated for the first symbol and
the second symbol.
8. A correcting method for timing recovery of a receiver, the
receiver comprising a timing recovery module that outputs a first
symbol and a second symbol, the correcting method comprising:
calculating channel impulse responses for the first symbol and the
second symbol to obtain a first set of peak times and a second set
of peak times, respectively; and calculating a correction signal
according to a relationship between the first set of peak times and
the second set of peak times, and sending the correction signal to
the timing recovery module.
9. The correcting method according to claim 8, wherein the step of
calculating the relationship between the first set of peak times
and the second set of peak times comprises: determining a first
peak time and a second peak time from the first set of peak times
and the second set of peak times according to the relationship
between the first set of peak times and the second set of peak
times, and calculating the correction signal according to a time
difference between the first peak time and the second peak
time.
10. The correcting method according to claim 9, wherein a
correction amount corresponding to the correction signal is
directly proportional to the time difference between the first peak
time and the second peak time.
11. The correcting method according to claim 9, wherein the first
peak time and the second peak time are times having largest
responses in the first set of peak times and the second set of peak
times, respectively.
12. The correcting method according to claim 9, wherein a relative
position of the first peak time in the first set of peak times is
same as a relative position of the second peak time in the second
set of peak times.
13. The correcting method according to claim 8, wherein the first
symbol and the second symbol are pilot signals.
14. The correcting method according to claim 8, wherein the first
set of peak times and the second set of peak times are times
corresponding to a plurality of peaks higher than a threshold when
channel impulse responses are calculated for the first symbol and
the second symbol.
Description
[0001] This application claims the benefit of Taiwan application
Serial No. 102120762, filed Jun. 11, 2013, the subject matter of
which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates in general to timing recovery of a
receiver, and more particularly to a feedback convergence mechanism
for timing recovery.
[0004] 2. Description of the Related Art
[0005] In modern communication technologies, both a transmitting
end and a receiving end employ a communication protocol or standard
understood by both parties to promote the communications between
the two parties. A signal transmitted by the transmitting end
passes through a transmission channel and is received by the
receiving end. In many communication protocol standards, a message
to be transmitted is transmitted in form of chucks. In different
communication protocols, these chucks may be referred to as
packets, symbols, or other terms. In the disclosure, for better
illustrations, these data chucks are referred to as symbols.
[0006] A communication protocol specifies a transmission speed or
timing of these symbols. In other words, the transmitting end knows
the speed according to which the symbols are to be transmitted, and
the receiving end is also aware of receiving the symbols at the
same speed. However, due to various realistic factors, the
receiving end may not be able to synchronize the reception timing
to be consistent with the transmitting end.
[0007] For example, a communication protocol standard may specify
that transmission is to be performed at a speed of 1000 symbols per
second. However, a clock oscillator at the transmitting end may not
generate a timing of exactly 1 KHz. In practice, a timing error
inevitably exists in the clock oscillator. In one ambient
temperature, the clock oscillator at the transmitting end may
exactly generate a perfect timing specified by the communication
protocol. Yet, due to heat energy generated by constant operations
of the transmitting end or a change in the ambient temperature, a
change in the timing generated by the clock oscillator is
unavoidably caused.
[0008] Similarly, the receiving end also requires a clock
oscillator to generate the timing specified by the communication
protocol. Same as the issue that the transmitting end encounters,
the clock oscillator at the receiving end may not perfectly
generate the timing specified by the communication protocol. In
other words, although the timing specified by the communication
protocol is 1 KHz, assuming that the transmitting end transmits the
symbols at a timing of 1.001 KHz, the receiving end is also
required to receive the symbols at a timing of 1.001 KHz. Assuming
that the transmitting end transmits the symbols at a timing of
0.999 KHz, the receiving end is also required to receive the
symbols at a timing of 0.999 KHz. Assuming that the receiving end
is limited to operate at a timing of 1 KHz, complications may arise
in the reception operations of the symbols.
[0009] FIG. 1 shows a schematic diagram of a signal propagation
model in the prior art. Signals are transmitted by a transmitting
end 110. These signals include multiple symbols, each of which
being represented by I.sub.k, where the subscript k represents a
serial number. A pulse shaping function P(x) outputs the symbols in
form of pulses, and a transmission time length required by each
symbol is T.sub.sym, tx. A signal sequence transmitted by the
transmitting end 110 is denoted as x(t).
[0010] The signal x(t) is transmitted via a channel 120 to a
receiving end 130. In real situations, the channel 120 is imperfect
as it receives distortion of a multipath effect h(t) and random
interferences. The latter is usually referred to as an additive
Gaussian white noise (AWGN), which is denoted as w(t).
[0011] Having passed through the distorted and interfered channel
120, a signal received by the receiving end 130 is denoted as y(t).
The signal y(t) is sampled by a sampling rate 1/Tsam to obtain a
sampled signal y(n). The sampled signal y(n) is forwarded by the
receiver 130 to a timing recovery module 132. An effect of the
timing recovery module 132 is to synchronize the timing to the
frequency for transmitting the symbols by the transmitting end 110,
such that y(n)=y(t)|.sub.t=n:Isym,rx. The signal y(n) having passed
through the timing recovery module 132 is forwarded to a subsequent
processing unit, e.g., an equalizer 134, to decode and obtain a
symbol . In an ideal situation, the symbol is equal to the symbol
I.sub.k transmitted from the transmitting end 110.
[0012] In general, the above sampling rate is usually faster than
the frequency at which the symbols are transmitted. With the timing
recovery module 132, the frequency is down-converted to the
so-called baseband. Therefore, a process for processing the signal
y(n) having passed through the timing recovery module 132 by a
subsequent processing unit is referred to as baseband
processing.
[0013] The above details describe an ideal signal propagation
model. As previously stated, the clocks generated by the clock
oscillators of the transmitting end 110 and the receiving end 130
are not necessarily the same. An event of same clocks generated by
the clock oscillators of the transmitting end 110 and the receiving
end 130 may be purely regarded as a coincidence. In other words, in
the signals sent from the clock recovery module 132, the time
T.sub.sym, rx occupied by each symbol received by the receiving end
does not perfectly equal to the time T.sub.sym, tx occupied by each
symbol transmitted from the transmitting end. After a period of
time, start time boundaries of the symbols may fail to align and
synchronize, such that the synchronization of the symbols may
become discrete and thus bring problems in the communication.
[0014] Therefore, to synchronize the timings of the transmitter end
110 and the receiving end 130, there is a need for a feedback
mechanism for the timing recovery module 132 to allow the receiving
end 130 to more precisely synchronize with the timing of the
transmitting end 110, i.e., to have T.sub.sym, tx to approximate
T.sub.sym, tx.
SUMMARY OF THE INVENTION
[0015] According to an embodiment of the present invention, a
correcting apparatus for timing recovery of a receiver is provided.
The receiver includes a timing recovery module that outputs a first
symbol and a second symbol. The correcting apparatus includes: a
channel pulse response module, configured to generate a first set
of peak times and a second set of peak times according to the first
symbol and the second symbol, respectively; and a calculation
module, configured to calculate a correction signal according to a
relationship between the first and second sets of peak times and to
send the correction signal to the timing recovery module.
[0016] According to another embodiment of the present invention, a
correcting method for timing recovery of a receiver is provided.
The receiver includes a timing recovery module that outputs a first
symbol and a second symbol. The correcting method includes:
calculating channel pulse responses of the first symbol and the
second symbol to obtain a first set of peak times and a second set
of peak times, respectively; and calculating a correction signal
according to a relationship between the first and second sets of
peak times, and sending the correction signal to the timing
recovery module.
[0017] The above and other aspects of the invention will become
better understood with regard to the following detailed description
of the preferred but non-limiting embodiments. The following
description is made with reference to the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a schematic diagram of a signal propagation model
in the prior art;
[0019] FIG. 2 is a block diagram of a receiving end according to an
embodiment of the present invention;
[0020] FIG. 3 is a detailed schematic diagram of a receiver end
according to an embodiment of the present invention;
[0021] FIG. 4 is a schematic diagram of a timing shift in a peak of
a channel pulse response according to an embodiment of the present
invention;
[0022] FIG. 5 is a schematic diagram of a timing shift in a peak of
a channel pulse response according to another embodiment of the
present invention;
[0023] FIG. 6 is a schematic diagram of a timing shift in a peak of
a channel pulse response according to another embodiment of the
present invention; and
[0024] FIG. 7 is a flowchart of a correcting method according to an
embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0025] Embodiments of the present invention are described in detail
below. Apart from the disclosed embodiments, the present invention
is also applicable to other embodiments. The scope of the present
invention is not limited by the embodiments, and is defined in
accordance with the appended claims. To better describe the
contents of the present invention to one person skilled in the art
and to keep the drawings clear, certain sizes and other associated
scales may be emphasized to appear exaggerated, with unrelated
details not entirely depicted.
[0026] A feature of the present invention is to provide a feedback
mechanism for timing recovery that is capable of correcting a
timing error within a short period. The feedback mechanism achieves
a precision of correcting every symbol and thus lowers
probabilities of reception errors and repeated transmission of the
symbols.
[0027] FIG. 2 shows a block diagram of a receiving end 230
according an embodiment of the present invention. A difference of
the embodiment from the receiving end 130 of the prior art is a
timing recovery module 232 and a timing recovery correcting module
236 for feeding back a timing recovery condition. Other symbols
correspond to the signal propagation module in FIG. 1, and
associated details shall be omitted herein.
[0028] In general, a communication protocol specifies signals or
symbols known to both the transmitting end 110 and the receiving
end 230, so as to assist the receiving end 230 in signal
acquisition and signal synchronization. A kind of the above signals
or symbols is pilot signal. Further, pilot signals may also be
utilized for channel estimation.
[0029] As both of the transmitting end 110 and the receiving end
230 know a format and arising positions of the pilot signals, the
pilot signals are frequently applied for synchronization. In
specifications of certain communication protocols, pilot signals
may continuous pilots or scattered pilots. For example, in the
Integrated Services Digital Broadcasting for Terrestrial Television
(ISDB-T) communication protocol, pilot signals may be continuous
pilots or scattered pilots consisted in form of symbols.
[0030] In the present invention, the above pilot signals, or any
symbols known to the transmitting end 110 and the receiving end
230, may be utilized for correction and feedback of timing
recovery. FIG. 3 shows a detailed schematic diagram of a receiving
end according to an embodiment of the present invention. In FIG. 3,
the timing recovery module 232 outputs multiple symbols that are
timing corrected. In addition to being forwarded to a subsequent
processing module, e.g., the equalizer 134, these symbols are also
sent to the timing recovery correcting module 236.
[0031] The timing recovery correcting module 236 includes three
secondary modules. A channel impulse response (CIR) module 310
first receives the symbols. The channel impulse response module 310
calculates a channel impulse response for each symbol. One person
skilled in the art can understand the calculation for the channel
impulse response, and such details shall be omitted herein.
[0032] If the timing recovery module 232 of the receiving end 230
correctly synchronizes with the symbol transmission rate of the
transmitting end 110, the channel impulse response of each symbol
reaches a high peak within a same period. For example, assuming
that the symbol transmission rates of the transmitting end 110 and
the timing recovery module 232 are synchronized at 1 KHz, at a time
point of 1/1000 second after the channel impulse response of a
previous symbol reaches a high peak, i.e., in exactly one period,
the channel impulse response of a next symbol also reaches a high
peak.
[0033] However, when the symbol rate of the timing recovery module
232 is faster than the symbol rate of the transmitting end 110, in
other words, when the symbol period of the timing recovery module
232 is shorter than the symbol period of the transmitting end 110,
the high peak of the channel impulse response of the next symbol is
delayed.
[0034] Conversely, when the symbol period of the timing recovery
module 232 is longer than the symbol period of the transmitting end
110, that is, when the symbol rate of the timing recovery module
232 is slower than the symbol rate of the transmitting end 110, the
high peak of the channel impulse response of the next symbol is
brought forward.
[0035] The above delayed and brought-forward times are associated
with the symbol periods of the timing recovery module 232 and the
transmitting end 110. Thus, by recording the times of the high
peaks of the channel impulse response of two or more symbols, it
can be learned whether the symbol period of the timing recovery
module 232 is fast or slow. Further, the difference between a fast
or slow symbol period and a correct symbol period can be calculated
to further send a correction signal to the timing recovery module
232, so as to allow the timing of the timing recovery module 232 to
converge to be substantially synchronized with the timing of the
transmitting end 110.
[0036] Hence, referring to the embodiment in FIG. 3, the timing
recovery module 236 may further include a peak recording module 320
and a calculation module 330. The peak recording module 320 records
peak times and/or response levels of the channel impulse responses
of multiple symbols. In one embodiment, multiple symbols refer to a
previous symbol and a next symbol. In another embodiment, multiple
symbols refer to a first symbol and an N.sup.th symbol subsequent
to the first symbol.
[0037] In the previous embodiment, the channel impulse response
module 310 calculates the channel impulse response for each symbol.
An advantage of such approach is that timing correction and
adjustment can be performed after receiving each symbol, and so the
timing of each symbol may closely synchronize with the transmitting
end 110. However, the calculation amount of such approach is much
more than that of the second embodiment. In a next embodiment, the
channel impulse response module 310 calculates the channel impulse
response for every N symbols, and involves a calculation amount of
1/N of the previous embodiment. However, such approach suffers from
a drawback that timing correction and adjustment can only be
performed for every N symbols. For N in a large value, an
asynchronous situation may arise in the N symbols. One person
skilled in the art can understand that, according to different
designs, different embodiments may be selected to design the timing
recovery correcting module 236.
[0038] In one embodiment, the peak recording module 320 may be
utilized to store all data generate by the channel impulse response
module 310, at least including the peak time, response level and
values of energy. In another embodiment, the peak recording module
320 may store a part of data. In another embodiment, the peak
recording module 320 may store all data calculated by the
calculating module 330, at least including the correction
signal.
[0039] After the peak recording module 320 records multiple peak
times of the channel impulse responses, the calculation module 330
may calculate a correction signal according to shift amounts and
shift directions of the peaks and an interval between multiple
symbols. The correction signal is fed back to the timing recovery
module 232. According to the correction signal, the timing recovery
module 232 corrects the frequency according to which its timing is
generated to further synchronize with the symbol rate of the
transmitting end 110.
[0040] FIG. 4 shows a schematic diagram of a timing shift in a peak
of a channel impulse response according to an embodiment of the
present invention. Two diagrams are depicted in FIG. 4. The upper
diagram represents a timing diagram of a peak of a channel impulse
response of a first symbol. The lower diagram represents a timing
diagram of a peak of a channel impulse response of a second symbol.
As previously stated, in one embodiment, the second symbol is a
symbol that closely follows the first symbol. In another
embodiment, the second symbol is an N.sup.th symbol subsequent to
the first symbol.
[0041] The vertical axis in each diagram represents a response
level of the channel impulse response, and the horizontal axis
represents a sampling time. One person ordinary skill in the art
can understand that, although the timing shift is represented in
form of diagrams, the peak recording module 320 may illustrate the
diagrams in FIG. 4 in any data form in actual designs. For example,
the diagrams in FIG. 4 may be illustrated by form of a table or a
two-dimensional array.
[0042] In the upper diagram of FIG. 4, it is indicated that the
first symbol corresponds to one response peak. In the lower
diagram, it is indicated that the second symbol also corresponds to
one response peak. However, the response peak in the lower diagram
has a shift compared to the response peak in the upper diagram,
meaning that the timing of the timing recovery module 232 and the
timing of the transmitting end 110 are asynchronous.
[0043] One person skilled in the art can understand that, although
the shift depicted in FIG. 4 is to the right, the shift may also be
to the left or no shift is present at all in actual possible
situations. When there is no shift at all, it means that the timing
of the timing recovery module 232 and the timing of the
transmitting end 110 are synchronous. In the above situation, the
calculation module 330 need not generate the correction signal, or
is only required to generate a correction signal with a correction
value of zero to be fed back to the timing recovery module 232.
When the shift is not zero, as previously stated, the calculation
module 330 may calculate a correction signal according to the shift
amount and the shift direction of the peak and the interval between
multiple symbols. The correction value represented by the
correction signal is directly proportional to the shift amount of
the peak.
[0044] FIG. 5 shows a schematic diagram of a timing shift in a peak
of a channel impulse response according to another embodiment of
the present invention. A difference between FIG. 4 and FIG. 5 is
that, the first symbol and the second symbol in FIG. 4 respectively
correspond to one response peak, and the first symbol and the
second symbol in FIG. 5 respectively correspond to multiple
response peaks. As previously described in the prior art, the
reason causing the first symbol and the second symbol to
respectively correspond to multiple response peaks is that the
channel 120 may be affected by the multipath effect h(t).
[0045] The multipath effect h(t) means that a signal transmitted
from the transmitting end 110 arrives the receiving end 230 via
multiple paths 120. Due to different lengths of these paths, the
time points at which the symbol signal arrive the receiving end 230
are different. Thus, for the same symbol, multiple response peaks
exceeding a threshold are generated after calculations performed by
the channel impulse response module 310. With the presence of
multiple response peaks, the calculation module 330 requires extra
efforts for calculations.
[0046] In an embodiment shown in FIG. 5, a first symbol in the
upper diagram and a second symbol in the lower diagram both pass
through three paths, and respectively yield three peaks after
calculations of the channel impulse response module 310. The three
peaks of the first symbol are denoted as 510a, 520a and 530a. The
three peaks of the second symbol are denoted as 510b, 520b and
530b. For illustration purposes, the peaks corresponding to the
first symbol are referred to a first set of peaks, which occur at a
first set of peak times. Similarly, the peaks corresponding to the
second symbol are referred to as a second set of peaks, which occur
at a second set of peak times.
[0047] According to relative positions of the peaks, the peak 510a
corresponds to the peak 510b, the peak 520a corresponds to the peak
520b, and the peak 530a corresponds to the peak 530b. Between the
upper diagram and the lower diagram, the distances between the
corresponding peaks are unchanged, and hence the above relationship
is obtained. Further, the second peaks 520a and 520b are the
highest of all three peaks, and the amount energy of signals
transmitted along this path is the largest. Thus, this path may be
regarded as a primary path, and the second peaks 520a and 520b may
be regarded as primary peaks. In the embodiment in FIG. 5, when the
primary peak 520a of the first symbol corresponds to the primary
peak 520b of the second symbol, the shift amount of the primary
peak may be utilized as a basis for calculating the correction
signal.
[0048] FIG. 6 shows a schematic diagram of a timing shift in a peak
of a channel impulse response according to another embodiment of
the present invention. A difference of the embodiment shown in FIG.
5 is that, the primary peak corresponding to the first symbol is
the second peak 520a, and the primary peak corresponding to the
second symbol is the third peak 530b.
[0049] When the shift amount between the primary peaks of the first
symbol and the second symbol is selected as the basis, the basis
calculated is a false shift amount between the third peak 530b and
the second peak 520a. Although the energy distributions of signals
along the three paths are changed to lead to changes in the
response peaks, the three paths however remain the same. If the
shift amount of the response peak between the two paths is
mistakenly regarded as the shift amount, a false shift amount is
obtained.
[0050] To prevent the above error, the calculation module 330 needs
to determine the relationship of the above peaks, and more
particularly the relative positions. When the relative positions of
the three peaks are unchanged, according to the relationship of the
relative positions of the peaks, the calculation module 330
determines that the peak 510a corresponds to the peak 510b, the
peak 520a corresponds to the peak 520b, and the peak 530a
corresponds to the peak 530b. Thus, in an embodiment shown in FIG.
6, the calculation module 330 calculates the shift amount between
the primary peak 520a of the first symbol and the second peak 520b
in the second symbol which corresponding to the peak 520a. That is,
the shift amount is a relative shift amount between the peak 520b
and the peak 520a.
[0051] In conclusion, in the embodiment in FIG. 5, the calculation
module 330 calculates the correction signal according to the shift
amount of the primary peak and the interval between two symbols. In
the embodiment in FIG. 6, the calculation module 330 first
identifies the relationship between the peaks, and then calculates
the correction signal according to the shift amount of the
corresponding peaks and the interval between two symbols.
[0052] One person skilled in the art can appreciate that, since the
relationship between the peaks needs to be first identified in the
embodiment in FIG. 6, the calculation amount of the embodiment in
FIG. 6 is larger than that of the embodiment in FIG. 5. Therefore,
in an embodiment of the present invention, when the shift amount
calculated in the embodiment in FIG. 5 exceeds a previously
calculated shift amount by a predetermined range, the method in the
embodiment in FIG. 6 is utilized instead to increase the
calculation amount and thus to prevent a false shift. In another
embodiment of the present invention, when the calculation in the
embodiment in FIG. 6 encounters the situation of FIG. 5, i.e., the
primary peak is not changed, the embodiment in FIG. 5 capable of
reducing the calculation amount can be utilized instead.
[0053] FIG. 7 shows a schematic diagram of a process of a
correcting method according to an embodiment of the present
invention. The correcting method begins with a channel impulse
response step 710 to perform a channel impulse response on multiple
timing-recovered symbols. The process then proceeds to a channel
impulse response recording step 720 to record one or multiple
response peaks and/or or peak times of the channel impulse response
of each symbol. In a correction signal calculating step 730, a
correction signal is calculated according to the response peak(s)
and/or peak time(s) and an interval between the symbols. The
correction signal is then fed back to a timing recovery
apparatus.
[0054] The symbols include a first symbol and a second symbol,
which may be pilot signals. In one embodiment, the second symbol is
a symbol that closely follows the first symbol. A correction amount
represented by the correction signal is directly proportional to
the peak time difference. In one embodiment, as shown in FIG. 4 and
FIG. 5, the peak time is the time having the largest response in
the channel impulse responses.
[0055] In another embodiment, as shown in FIG. 6, when multiple
peaks higher than a threshold are present in the channel impulse
response, before calculating the peak time difference, the peaks of
first symbol and the second symbol are corresponded, and the peak
time difference is calculated according to the time difference of
the corresponding peaks. Wherein, the peak time difference may be
the time difference between the highest peak of the first symbol
and the corresponding peak of the second symbol. In another
embodiment, the peak time difference may be the time difference
between any peak of the first symbol and the corresponding peak of
the second symbol.
[0056] While the invention has been described by way of example and
in terms of the preferred embodiments, it is to be understood that
the invention is not limited thereto. On the contrary, it is
intended to cover various modifications and similar arrangements
and procedures, and the scope of the appended claims therefore
should be accorded the broadest interpretation so as to encompass
all such modifications and similar arrangements and procedures.
* * * * *